Obese children require smaller doses of the general anesthetic (GA) propofol than non-obese children do to bring about a safe level of unconsciousness, according to a new study.

Researchers at the Texas Children's Hospital (Houston, USA) conducted a study involving 40 obese and 40 non-obese children using a process called the biased coin design, which requires fewer patients and provides a more accurate calculation of dose requirements than older techniques. After measuring each child's response 20 seconds after receiving propofol, it was determined that obese children needed 2 mg/kg of propofol to bring about unconsciousness at the beginning of surgery, compared to normal weight children who needed 50% to 60% more propofol (3.2 mg/kg).

The researchers explained that since propofol can cause prolonged sleepiness and decreased breathing, it is important for anesthesiologists to consider whether the anesthetic drug dose delivered should be based on the child's actual weight or on his lean body weight. In obese children, 75% of excess body weight consists of fat tissue, which alters drug distribution. The study was presented at the American Society of Anesthesiologists (ASA) annual Anesthesiology meeting, held during October 2011 in Chicago (IL, USA).

“These study findings mean that when providing care for obese children with propofol, 95% of children will likely need only a smaller dose of propofol to initiate anesthesia for surgical procedures,” said lead author and study presenter Olutoyin Olutoye, MD, MSc. “This is important as propofol may cause low blood pressure, an effect that can be worsened if larger-than-needed amounts are given.”

Propofol is a short-acting, intravenously administered hypnotic agent. Its uses include the induction and maintenance of GA, sedation for mechanically ventilated adults, and procedural sedation. Propofol is unrelated to barbiturates and it has largely replaced sodium thiopental (Pentothal) for induction of anesthesia since recovery from propofol is more rapid and unambiguous when compared with sodium thiopental.

 

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